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Objectives of the Conference

To provide an open platform that will enable a wide range of institutions/agencies, including national and international bodies; governmental and non-governmental organizations, research institutes/universities and development organizations to share information and exchange ideas, views and experiences on approach and methodology for assessment of soil nutrient depletion and requirements.

Background to the Conference

Nutrient depletion is one of the major forms of soil degradation. Continuous cropping without adequate restorative practices may pose threats to the sustainability of agriculture. A quantitative knowledge on depletion of plant nutrients from soils helps to understand the state of soil degradation and may be helpful in devising nutrient management strategies. Nutrient balance exercises may serve as instruments to provide indicators for the sustainability of agricultural systems.

Nutrient budget and balance approaches have been widely applied in the recent past. Studies have been undertaken at varied levels ranging from plot, farm, regional, national to supra-national. Widespread occurrence of nutrient mining and soil fertility decline has been reported.

Most of the nutrient balance studies provide quick findings, based on a short time-frame exercise, and have necessarily to depend on a number of assumptions relating to system dynamics. Nutrient depletion exercises adopting static system models of inputs and outputs, and based on linear relationships for upscaling, provide little insight into the dynamics and the processes involved. Aggregate nutrient budgets do not reveal the true picture and depict a biased scenario. The issues of spatial and temporal variability further add the elements of doubt to the reliability of the aggregate nutrient balance estimates as a basis for policy decisions. Methodological estimations are fraught with numerous problems such as limited availability of data at spatial scales, scale-specific spatial variation of nutrient balance input data, non-linearity in upscaling and lack of reliable upscaling techniques. Implied uncertainties, scale-dependence coupled with data collection problems, provide the nutrient balance studies with a complexion of complicated exercise and deprive them from attaining the simple objective indicators of sustainable soil productivity.

Nutrient budgets may be useful for identifying the faults of present systems, but the extrapolation of present deficits forwards, and ensuring their validity for the future presents practical problems. Further, the nutrient budgets tend to generate average estimates, whereas farmer strategy and management makes use of and develops diversity, constituting a fundamental difference in paradigm.

Soil nutrient balance studies might indicate nutrient losses from the system and do delineate the consequences of farming for soil fertility in a systematic manner, however, plausible solutions could be elusive.

The conference outcome would be useful in the development of more appropriate, reliable and simple nutrient depletion assessment models, adaptable to various situations.

A number of approaches and methods evolved by various agencies for different situations have been used for nutrient balance studies. A desk-study with the objective in view, would not only be a time and resource intensive process, but might not be able to capture some very useful experiences. Therefore, it is intended to facilitate the process with the help of this electronic communication. A background document 'Review on Assessment of Soil Nutrient Depletion and Requirements - approach and methodology' has been prepared. Though by no means it is exhaustive, it attempts to provide a brief gleaning in the prevalent approaches and methodologies and is intended to be a starting point for discussions, and receiving further contributions.

The main document "Review on Assessment of Soil Nutrient Depletion and Requirements - approach and methodology " is available as 'PDF' and 'WORD' file:

pdf file

Word file